Derivative Instruments Offsetting Balance Sheet (Details) (Derivative [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Offsetting Assets [Member]
Offsetting of Financial Assets and Liabilities [Line Items]
Gross Amounts of Recognized Financial Instruments	$ 87,728	$ 73,535
Gross Amounts Offset in Statement of Financial Position	(67,715)	(73,535)
Net Amounts of Assets Presented in Statement of Financial Position	20,013	0
Financial Instruments And Collateral	(18,099)	0
Net Amount	1,914	0
Offsetting Liabilities [Member]
Offsetting of Financial Assets and Liabilities [Line Items]
Gross Amounts of Recognized Financial Instruments	57,131	94,580
Gross Amounts Offset in Statement of Financial Position	(57,131)	(72,822)
Net Amounts of Assets Presented in Statement of Financial Position	0	21,758
Financial Instruments And Collateral	0	(24,491)
Net Amount	$ 0	$ (2,733)